Such flow control devices serve in particular to control the distribution of flow between the tubes of a tube bank in a heat exchanger, when one wishes to cause less flow in some tubes than in others, the amount of heat transferred through the first tubes intended to be less than through the other tubes according to the flowrate or temperature of the fluid impinging on the outside surface of the tubes. This case occurs in particular in heat exchangers in which highly pressurized heating steam flows through a tube bank in several successive passes, exchanging heat with firstly a relativey cold fluid, then a partly heated fluid.
The metal of the insert must exhibit specific characteristics enabling easy expansion in the tube of a bank or in the hole of the tube sheet corresponding to this tube, and must have a coefficient of expansion approximating that of the exchanger tube in order to avoid debulging from the effect of temperature cycling. It must also be able to substantially withstand erosion-corrosion from saturated steam leaving the orifice plate due to the high velocites attained in the orifice. Only very expensive alloys exhibit all of these properties combined.
It is the object of the present invention to provide a control device that is easy to secure within the heat exchanger tube or the corresponding orifice of a tube sheet by expansion, which also exhibits an outstanding resistance to erosion-corrosion from the steam which must flow therethrough.